1. Field of the Invention
The present invention relates to a novel silver halide photosensitive material for color photography providing an ornamental image, and a method for forming a color image using the same.
2. Description of the Related Art
Photosensitive materials for photography utilizing a silver halide are increasingly being developed recently, and at present, a color image having high image quality is easily available. For example, ordinary, in a method called color photography, photography is conducted using a color negative film, and image information recorded on a color negative film after development is printed optically on color photographic paper, to thereby obtain a color print. Recently, this process has developed to a high degree, and color laboratories that are large centralized apparatuses for producing large amounts of color prints with high efficiency and so-called miniature laboratories that are compact and simple printer processors placed in shops are now widely spread. As a result, any one can enjoy color photography easily.
Thus, while a system utilizing a silver halide (hereinafter, referred to as "silver halide system") have been developed, means by which digital image information is output via a personal computer and the like have also been developed to a remarkably degree. Though the silver halide system has reached a stage wherein simple and quick treatment is possible, it requires a specialized processing device using special processing solution such as developing solution, bleach-fix solution and the like and skilled operators. Meanwhile, an inkjet method, electrophotography method and sublimation type transfer method are spreading in offices and families as a system for obtaining a color image easily. Further, image quality obtained in these systems is recently excellent, and selling competition is intense to attract users with so-called "photographic quality". However, it can not be admitted yet that the outputted image in these systems has leached the same level as that of the silver halide system, though it has improved to a certain extent. Therefore, it is strongly required that the high quality image that is characteristic of the silver halide system be obtained with the same ease as in other systems.
Simply stated, the constant on the silver halide system represented by color photography is that processing with a specialized color laboratory is necessary. When use in offices and general households is considered, the ordinary silver halide system has a defect in that it has a complicated and time-consuming processing method. The reason for this is that, for example, when a color print is made using color photographic paper, a specialized color printer for printing color negative information on photographic paper while maintaining a suitable color balance is required. Further, to operation the color printer, skilled operators are usually necessary. Next, to treat the exposed color photographic paper, a color processor is required for conducting color development, bleach-fixing, and washing or stabilization processing under strictly controlled conditions, and for this treatment, a time of about 4 minutes is usually required. Moreover, the environmental load that has been recently observed cannot be ignored. Namely, processing solutions thereof contain substances whose discharge should be restricted such as color developing agents, iron chelate compounds which are bleaching agents, and the like, and developing equipment often require exclusive facilities.
Therefore, if these processes can be effected simply and quickly, it is expected that the high quality characteristic of the silver halide system can be utilized for output of color images in various fields. Namely, simple and quick processing is an important subject for further developing the silver halide system.
In view of this background, there have been suggested many improved technologies for making a system that uses neither a color developing agent nor a bleaching agent, which are used in current color image forming systems.
For example, in IS & T's 48th Annual Conference Proceedings, p. 180, a system is disclosed which removes developed silver and an unreacted silver halide by allowing a pigment formed in a developing reaction to migrate into a printing layer and then releasing the layer, making a bleach-fix bath, which is essential for conventional color photography processing unnecessary. However, in this suggested technology, a developing process in a processing bath containing a color developing agent is still necessary, and it can not be said that the environmental problem has been solved.
As a system requiring no processing solution containing a color developing agent, a pictrography system is provided by Fuji Photo Film Co., Ltd. In this system, a development reaction is caused by supplying a small amount of water to a photosensitive member containing a base precursor, laminating this with an image receiving member, and heating the laminate. This method is advantageous in that the above-described treatment bath is not used.
Pigment image formation by pictrography is roughly divided into a method in which a compound which releases a pigment in a developing reaction of exposed silver halide particles is used and the pigment is released corresponding to development, and a method in which a pigment is released reverse-corresponding to development by consuming a compound in which an oxide of a contained developing agent generated accompanying development of a silver halide causes a pigment releasing reaction. In both of the methods, a so-called pre-formed dye compound containing a pigment part previously in the molecule is taken into a photosensitive member. Consequently, in both methods, a colored material shall be contained in a photosensitive emulsion layer, and imparting high sensitivity is difficult. Further, compounds used in these color developing methods require complicated molecular structures for precisely controlling the above-described reactions, and are disadvantageous in terms of cost.
Since further development of a quick and simple image forming system can be expected by solving these problems of the pictrography method, development of novel technologies has been desired. As an example of such novel system, Japanese Patent Application Laid-Open (JP-A) No. 9-152705 discloses a technology for forming an ornamental image using a developing agent which can thermally develop a silver halide and a compound that releases a pigment through a coupling reaction with an oxide thereof.
Investigation has been conducted on a system for simply obtaining a color print having high quality in a short period of time based on the above-described technologies, and as a result, it has been found that image concentration varies according to variation in the amount of water used in thermal development, and that strict control of the amount of water is necessary for stably forming an image having high quality.
In such an image forming method, a small amount of water is used for the purpose of progressing a thermal developing reaction quickly. In detail, the developing reaction and the pigment releasing reaction are caused by heating in the presence of water between a photosensitive material and a pigment fixing material which fixes a generated pigment, the amount of water being in an amount corresponding to 1/10 to 1-fold of that required for the maximum swelling of a layer composed of these materials. In this procedure, variation in reaction amount of development or pigment release, which accompanies variation in the amount of water is not preferable for stably forming an image having high quality. Namely, it has become clear that when the amount of water varies, there is the fear that an image having constant quality can not be obtained repeatedly or that image concentration varies in one image and the like. Further, these problems regarding variation in image concentration, increasingly worsen when the temperature is raised to shorten processing time.